Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
DF: Fachverband Dielektrische Festkörper
DF 2: Nonlinear dielectrics, phase transitions, relaxors
DF 2.3: Vortrag
Montag, 14. März 2011, 11:40–12:00, KÖN Farb
Structural transformations in relaxor ferroelectrics on the mesoscopic scale — •Bernd J. Maier1, Boriana Mihailova1, Evgeniy A. Dul’kin2, Tim Prüßmann1, Carsten Paulmann1, Marin Gospodinov3, and Ulrich Bismayer1 — 1Mineralogisch-Petrographisches Institut, Universität Hamburg — 2Faculty of Science, The Hebrew University of Jerusalem, Israel — 3Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria
Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) is a canonical relaxor, undergoing on cooling a series of structural transformations without developing long-range ferroelectric order. Recently, it has been established that perovskite-type relaxors exhibit a characteristic temperature T⋆, at which initially formed polar clusters slow down and merge into larger polar nanoregions (PNRs). For PBST the temperature T⋆ is near 490 K as revealed by Raman scattering (RS) and acoustic emission (AE). RS data indicate that the transformation processes near T⋆ are realized via coupling of off-centred octahedral cations from adjacent polar clusters. AE experiments reveal that the coupling is highly anisotropic and is strongest along ⟨110⟩ cubic directions. AE measurements also demonstrate a temperature hysteresis of ∼15 K. Since PNRs generate strong x-ray diffuse scattering (XDS) along the ⟨110⟩⋆ directions, the XDS intensity was used as an order parameter to determine the thermodynamical character of the phase transformation occurring at T⋆. The temperature evolution of XDS in PBST measured with synchrotron radiation reveals a near-tricritical behaviour in terms of the Landau theory.